MCH K305D Power Supply

I just received a neat little switch-mode power supply in the post from Banggood, the K305D.

This neat supply runs up to 30 volts output (fully adjustable) and up to 5 amps (constant voltage or constant current) with 0.01v resolution and 0.001a resolution on the blue LED displays. The unit comes complete with simple test leads, mains lead and 8-sided “operation manual”. The – connection can optionally be grounded.

Right now I can’t test it to the limits but it works just fine running a new Raspberry Pi 3 B+. The unit arrived solidly packed and will make a fine addition to my somewhat overcrowded workspace.

Please note that in 2015, XJet (YouTube) did a write up on one of these and having used it for some time, noted poor build quality and issues with current limiting.

Well in 2018, mine seems to work just fine including the current limiting and taking into account that this is not an expensive supply, build quality on mine is not bad. I might’ve made the cables to the output terminals a little shorter and thicker personally but for what this supply is likely going to be used for, they should be just fine.

You should hook it up to a scope and look for overshoot in a variety of situations. I got a different brand switch mode bench supply and it turns out it sends out a quick pulse at relatively high voltage when you turn the supply off, regardless of whether or not the output was enabled and not dependent on the set voltage when you turn it off. It's a very short pulse (probably caps discharging) so most things probably won't care, but it fried an STM32 board I had hooked up directly to the 3.3V rail and will kill other sensitive devices.

When I emailed them about the issue they said "oh yeah that's to be expected" :/ It's a bit of a shame because I actually like it otherwise, just have to be careful to disconnect anything before turning it off.

If I had access to my test kit ~I would do just that. Perhaps in a few weeks. Regular readers will know that thanks to the unfortunate combination of having a stroke, smack in the middle of a house move, only to get the runaround from tenants currently occupying the home we're moving into, means that I've been without access to some of my top test kit for some time including scopes, logic analysers, my dummy load and much more. Hopefully very soon things will change and I will in fact do some more "normal" testing.

Bought one of these last summer. Never saw this video when I was researching one for my work bench. Co-worker bought the same unit and things seem to work, the limiting works fine. Maybe I should open it up (or not)!

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